Pneumatic tire construction

ABSTRACT

A tire construction in which continuous loops of reinforcement cords are placed in the tread portion of the tire to achieve greater tread stability and strength and provide greater resistance to tread peel.

United States Patent [72] Inventor William G. Cole 6400 Jocelyn HollowRoad, Nashville, Tenn. 37205 [21] App]. No. 811,563

[22] Filed May 28, 1969 [45] Patented Sept. 28, 1971 [54] PNEUMATIC TIRECONSTRUCTION 17 Claims, 10 Drawing Figs. [52] U.S. C1 152/361 [51] Int.Cl 1360c 9/18 [50] Field of Search 152/361 [56] References Cited UNITEDSTATES PATENTS 3,131,744 5/1964 Boussu etal 152/361 3,205,931 9/1965Keefe, Jr. 152/361 X 3,231,000 1/1966 Massoubre 152/361 3,310,093 3/1967Frazier [52/361 3,335,777 8/1967 Hutch 152/361 3,441,074 7/1969Pouilloux et a1. 152/361 Primary Examiner-Milton Buchler AssistantExaminer-Carl A. Rutledge Attorney-Oberlin, Maky, Donnelly and RennerABSTRACT: A tire construction in which continuous loops of reinforcementcords are placed in the tread portion of the tire to achieve greatertread stability and strength and provide greater resistance to treadpeel.

PATENTEU SEP28 ISYI PATENIED SEPZ 8'19?! sum 2 or 3 INVENTOR 9 v WILL/AMa. COLE BY ammly awdlyam ATTORNEYS PATENIEB sma ma sum 3 or 3 INVENT ORWILLIAM G. COLE I iTTORNEYS PNEUMATIC TIRE CONSTRUCTION BACKGROUND OFTHE INVENTION The present invention relates generally as indicated topneumatic tire constructions, and is particularly concerned with themanufacture of retarded tires, but it will be apparent that certain ofthe principles and techniques involved are also applicable to new tireconstructions.

After the tread of a tire is completely worn, the tire carcass or casingmay still be in relatively good condition, which oftentimes makes iteconomically practical to replace the worn out tread with a new oneusing conventional retreading techniques to extend the useful life ofthe tire. The used tire to be retreaded is first inspected for defectsof a structural nature, and if it passes inspection, the tire is mountedon a power driven rotatable mandrel and inflated to assume its normaloperating configuration. Then the tire is precisely fed into a powerdriven circular-shaped rasp which uniformly cuts off the old tread,leaving the tire with a smooth buffed outer surface which has areasonably uniform surface thickness in the area to be retarded. If onlya top cap tread is to placed on the tire, buffing is confined to thetread area, whereas if a full retread is required, the buffing iscontinued down each sidewall for about one-fourth the thickness of thetire in the radial direction. After the tire has been properly buffed,it is transferred to a tire-building machine and the buffed surface isbrush or spray coated witha uniform coating of a suitable airdryingcement. Before the cement has completely cured, the tire-buildingmachine is caused to rotate the tire slowly, and at the same time astrip of die sized rubber or camel back having the proper width,thickness and tapered design for the specific tire being retreaded isfed onto the tire and forcibly pressed into place using specificallyshaped rotating rollers to firmly and smoothly adhere the rubber to theold buffed casing. When a single complete wrap of the die sized rubberis completed, it is cut off and the ends are butted and stitchedtogether in conventional manner.

Alternatively, the buffed tire may be mounted on a stripwinder machineand the tire continuously rotated as a ribbon of extruder produced andsized rubber is fed out and pressed against the buffed tire surface. Theribbon is applied to the tire in a continuous spiral fashion until therequired amount of rubber for the retread is in place.

In any event, whether the tread rubber is applied in a single wrap orconsists of a plurality of wraps of extruded rubber, afterwards the tireis fitted with a curing tube and inner curing rims inserted into amatrix or mold to which heat and pressure are applied for curing orvulcanizing the new rubber and adhering the new rubber to the old buffedand cemented surface. During the curing operation, the desired treaddesign is applied to the tread rubber. Then the tire is removed from themold and the inner curing rims and curing bag are stripped off. Finally,the tire is inspected, and ready for use.

As apparent from the above, the complete retreading process isrelatively simple and inexpensive as compared to the manufacture of newtires, primarily because the quality considerations for a retread tireare neither as numerous nor as stringent as in the case of a new tire.When a used tire is received for retreading, it has already beenthermally conditioned by use and has been stretched until it has assumedthe final configuration that it will retain for its retreaded life.Further, the original tire design presumably contained all of thestress-resisting members that were deemed necessary for its class andtype of service, and therefore it is not required of the retreader thathe build into the retreaded tire any additional strength.

The basic function of the retreader is simply to place on the worn tirea new rubber tread to enhance the service life of the tire which can bedone at considerably less cost than the cost of a new tire. However, inthe past such reduced cost has been offset to a greater or lesserextent, and in some instances completely negated because of the normallyshorter life of a retreaded tire as compared to a new tire in use, andthe tendency of the tread portion of a retread to peel off.

Premature failure of a retreaded tire due to tread peel is normallycaused by separation of the retread rubber from the buffed surface ofthe original tire either due to a breakdown of the adhesive bondtherebetween or a combination of tread injury and centrifugal force.This type of failure has sharply increased particularly with respect totruck tires because of increased highway speeds and load allowances, somuch so in fact that many trucking concerns no longer consider iteconomical or safe to use retreaded tires.

Tread peel is not ordinarily a problem in new tires since the treadrubber, plys, and sidewalls are vulcanized in a single operation toprovide a unitary tire construction which does not depend on an adhesivebond between newly vulcanized rubber and an old vulcanized surface as inthe normal retreaded tire construction.

The strength, stability, and resistance to deformation and wear of newtire treads are also much greater than conventional retreads because ofthe use of one or more reinforcement belts or bands composed of mutuallyparallel cords of substantially continuous glass or other reinforcementfilaments disposed between the tire casing and tread rubber of a newtire. Due to the unitary nature of the tire rubber of a new tire aftervulcanization, such reinforcing belts reduce substantially the amount oftread squirm thus resulting in improved tread wear and stability of thetread with respect to its gripping action on the road surface, which isnot normally obtained when the same tire is retreaded in conventionalmanner.

Similar improvements in strength and wear of retreaded tired can beobtained by circumferentially wrapping one or more strands of fiberglassreinforcement cord in spiral manner around a previously buffed tireuntil a sufficient quantity has been placed on the tire or by wrappingreinforcement belts composed of mutually parallel cords of glass strandsaround the tire and then covering the reinforcement cord or belts withnew tread rubber which is vulcanized in place in conventional manner.However, it has been found that the layers or belts of glass fibersserve to decrease rather than increase the ability of the retreaded tireto resist peel or separation of the retread rubber from the originalbuffed surface. This is primarily due to the inability of the retreadrubber to penetrate and properly contact the buffed tire surface throughthe spirally wrapped fiberglass cord or belts. If an extremely lightlayer of fiberglass cord were spirally wrapped in this fashion it mightbe possible to separate the strands or cords in such a manner as toavoid contact with each other and thus obtain good penetration of thenew retread rubber between the cords, in which event adequate adhesionbetween the new tread rubber and old tire could be achieved. However,the quantity of cord required to be used for proper strength of theretreaded tire is such that the individual cords of the spiral wrappingscannot readily be kept separated. The cords invariably arrangethemselves in a close contact, shoulder to shoulder fashion, or aresuperimposed on each other in such fashion that they prevent adequateretread rubber penetration, whereby the ability of the retreaded tire toresist peel of the newly cured retread rubber is oftentimes notadequate, particularly under present day high-speed, high-loadconditions placed on truck tires.

As an example, in the retreading of a typical heavy-duty truck tire itis desirable to use approximately 2 pounds of fiberglass tire cord toachieve the required tire strength. The cord itself may vary inconstruction, but a typical tire cord would be one designated at75/5/O.,One pound of this cord contains approximately 1,275 yards orsufficient cord to wrap around a buffed 10.00X20 tire 383 times. Twopounds of the same material will provide approximately 763 individualturns around the buffed casing. When arranged in a closely nestedshoulder to shoulder fashion, 30 individual cords measure one inch wide.Thus, a single cord thickness of the desired quantity of cord materialwrapped around the buffed casing would be 25.5 inches wide. Since thedesired wrap surface on a tire of this size is a maximum of 9 inches, itis obvious that almost three layers of individual cords must be used inorder to achieve the desired reinforcement. However, if three plys oftightly nested, shoulder to shoulder individual cord thickness materialis wrapped around the tread portion of a tire, it is substantiallyimpossible to secure satisfactory penetration of the retread rubber tothe buffed surface. The major portion of the adhesion developed by thismethod is between the new retread rubber and the outer ply of spirallywrapped fiberglass tire cord. Relatively little adhesion of the firstsingle-cord thickness layer or belt to the original tire buffed surfaceis obtained, and relatively little inner layer adhesion occurs betweenthe three plys of spirally wound fiberglass cord. Thus, a retreaded tireproduced in this fashion, while having some desirable characteristics ofstrength, is more prone to failure by tread peel than a conventionallyretreaded tire.

A restrictive band of elastomeric material has previously been woundabout the buffed casing contemporaneously with applied filament woundcord, but this still does not solve the problem of inadequatepenetration of the elastomeric material between the individual cords,and the elastomeric material itself completely eliminates contact of theretread rubber with the buffed casing. Moreover, in one of the previousknown tire retreading methods are the reinforcement cords placed withinthe retread rubber itself where their high hoop strength will providethe greatest resistance to tread peel and yet not interfere with thedesired adhesive bond between the retread rubber and buffed tire casing.

SUMMARY OF THE INVENTION With the foregoing in mind, it is a principalobject of this invention to provide novel tire constructions,particularly retreaded tires, including a reinforcement cord system forthe tread portion which imparts greater service life, impact strength,and puncture resistance thereto, and also provides increased tread peelresistance.

Another object is to provide such a tire construction in which both amechanical interlock and adhesive bond is obtained between the retreadrubber and buffed tire casing.

These and other objects of the present invention are achieved byproviding a tire construction in which reinforcement cords are placed inthe tread rubber where they will not interfere with the adhesive bondbetween the tread rubber and buffed casing. In fact, the reinforcementcords are greatly resist tread peel because of the mechanical interlockbetween each of the individual cords and the tread rubber. In one formof the invention, the reinforcement cords are spiral would directly ontothe cement coated buffed tire casing to provide a plurality of layers,each layer consisting of a plurality of mutually parallel uniformlyspaced apart cords placed in zigzag fashion with the cords in each layercrisscrossing each other to provide an open mesh multilayered pattern orlattice work into and through which the retread rubber is forced duringvulcanization. The retread rubber thus applied surrounds the individualcords to provide a mechanical interlock therebetween as aforesaid, andalso directly contacts the buffed surface over a large area to achieve asubstantial adhesive bond.

Alternatively, the desired zigzag cord pattern may be preplaced onrelease paper or embedded in a continuous ribbon of elastomeric materialand subsequently applied to the buffed tire casing, thus eliminating theneed for the retreader having to purchase the necessary equipment forlaying the cord pattern himself.

While the invention is primarily concerned with the manufacture ofretreaded tires, it will be appreciated that certain of the principlesare also applicable to new tires, particularly in the placement of thereinforcement cords directly in the tread portion to provide increasedhoop strength and stability in the tread portion of the tire.

To the accomplishment of the foregoing and related ends, the invention,then comprises the features hereinafter fully described and particularlypointed out in the claims, the following description and the annexeddrawings setting forth in detail certain illustrative embodiments of theinvention, these being indicative, however, of but a few of the variousways in which the principle of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS ln the annexed drawings FIG. 1 is afragmentary radial section through a preferred form of tire constructionmade in accordance with the present invention;

FIG. 2 is a fragmentary radial section of the tire construction of FIG.1 but with the tread portion removed to show the arrangement ofreinforcement cords around the tire casing;

FIG. 3 is a fragmentary to plan view of the tire construction of FIG. 2,taken on the plane of the line 3-3, to show the crisscross pattern ofthe various reinforcement cord layers;

FIGS. 4 and 5 are respectively schematic top plan and side elevationviews illustrating the manner of applying the reinforcement cords to thebuffed tire casing as shown in FIGS. 1 through 3;

FIGS. 6 and 7 are respectively schematic top plan and side elevationviews illustrating a manner of applying reinforcement cords to releasepaper in a desired pattern;

FIG. 8 is a schematic side elevation view showing a manner oftransferring the reinforcement cord pattern from the release paper ofFIG. 7 to be buffed tire casing;

FIG. 9 is a schematic side elevational view showing a manner ofembedding reinforcement cord in a continuous strip of elastomericmaterial and winding the same around a buffed tire casing; and

FIG. 10 is a fragmentary radial section showing a tire construction madein accordance with the method illustrated in FIG. 9 prior tovulcanization of the tread rubber.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now in detail to thedrawings and first to FIGS. 1 through 3, there is shown a pneumatic tireI which may be of any conventional type for use on passenger cars,trucks, or offthe-road equipment, including a carcass or casing 2consisting of one or more plys 3 and sidewalls 4. One or more of theplys 3 may contain reinforcement cords of fiber glass or otherreinforcement material. The tire is shown with its original treadportion removed after substantial wear to prepare the tire forretreading in a manner to be subsequently fully explained. Removal ofthe tread is preformed with the tire I properly inflated and mounted ona rotating mandrel precise feeding of the tire into a power drivencircular-shaped rasp which uniformly cuts off the old tread withoutinjuring the carcass plys, thus leaving the tire with a smooth buffedouter surface Normally, the new retread runner is simply adhered to theouter buffed surface 5 using a suitable air drying cement and thenvulcanized in a conventional vulcanizing mold. However, there has beenconsiderable objection to such retreaded tires because of prematurefailure due to tread peel, which is most frequently caused by abreakdown of the adhesive bond between the tread rubber and tire casingand the high centrifugal which results when the tire is driven at highspeeds and under high loads tending to separate the tread rubber fromthe tire casing. Such failures are particularly prevalent with retreadedtruck tires due to increased highway speed and load allowances fortrucks. The normal life of a retreaded tire made in accordance withprevious practices is also much shorter than the normal expected life ofa new tire tread in use. These two factors and the safety hazardscreated thereby have greatly limited the use of retreaded tires, despitethe apparent economics of retreading.

It has been found, however, that if a plurality of layers ofsubstantially continuous reinforcement cords are circumferentiallyspirally wrapped around the buffed tire in accordance with thisinvention before the retread rubber is applied, the tread peelingdeficiencies previously described will be eliminated, and, moreover, theretreaded tire will have a greatly enhanced service life and greaterimpact strength and puncture resistance. Although the reinforcement cordis preferably made of fiberglass, it will be apparent that otherreinforcement cord materials may also be used, including synthetic andnatural fiber materials and metallic wire or cord.

More particularly, and as clearly shown in FIGS. 1 through 3, eachreinforcement cord layer 6 consists of one or more closely spaced apartmutually parallel cords 7 which have been wound in a symmetrical oruniform zigzag pattern so that adjacent layers crisscross each other toprovide an open mesh multilayered reinforcement cord system in which theindividual cords or strands are separated or isolated from each otherexcept for the contact points where the cords in each succeeding layercross over the cords of the previously deposited layer.

The individual fiberglass cords 7 in each layer 6 are sufficientlyspaced from each other to provide a substantial open area between cordsso that preferably between one-third to two-thirds of the area of eachlayer is left open to permit the soft new retread rubber 8 which issubsequently forcibly pressed onto the tire to penetrate into andthrough the cord layers 6 to obtain the desired adhesion between theretread rubber 8 and buffed tire casing 1. If 75/5/0 tire cord is used,a spacing of approximately 10 cords per inch of width will provideadequate open area for effective penetration of the thread material.

Because the cords of each successive layer crisscross each other, asaforesaid, they will always maintain the desired open mesh pattern andwill not rearrange themselves in a close contact, shoulder to shoulderfashion, as would likely happen if the cords were simply spirally woundonto the casing in the usual nonzigzagging manner. Another advantage ofproyiding an open mesh pattern is that it enables the new tread rubberbeing applied to surround each of the individual cords 7 in each layer 6and thus provides a mechanical interlock therebetween as well as anadhesive bond. Accordingly, the reinforcement cords 6, which have a veryhigh loop strength, will greatly assist in retaining the tread rubber 8against peel off. Moreover, because of the mechanical interlock betweenthe retread rubber and cords produced by the open lattice work,atmospheric or chemical variations which might serve to deteriorate theeffectiveness of the chemical adhesive bond between the retread rubber,buffed tire surface, and reinforcement cords will not in any way disturbthe effectiveness of the reinforcement cords in holding the retreadrubber in place. Another advantage obtained in locating thereinforcement cords directly in the retread rubber itself-instead ofbetween the tire casing and retread rubber is that the reinforcementcords will more effectively eliminate tread squirm which is the primarycause of short tread life. Placement of the reinforcement cordsoutwardly within the tread of a new tire may also be advantageously usedto strengthen the tread portion and reduce squirm.

Although the angle of wrap a of the cords 7 which continuously reversearound the buffed tire with respect to the peripheral center line of thetire at any given point may vary substantially depending upon thecircumference of the tire (the greater the circumference, the smallerpermissible angle), the width of the surface being rapped, and width ofthe wrap itself, it is preferred that such angle be as small aspractical without disturbing the desired open mesh pattern of theindividual layers of cords, since a zero wrap angle produces the maximumstrength in the hoop direction by placing the strands in pure tensionand provides maximum improvement in tread life. However, at extremelylow angles, it is difficult to secure effective cord crossover since thecords in adjacent layers tend to push each other aside and becomeparallel. As a practical matter, it has been found that angles of fromslightly less than 1 to approximately 12 will provide the desiredcrossover patter and still achieve sufficient hoop strength for longtread life.

One preferred method of applying the reinforcement cords 7 to the buffedtire I is schematically illustrated in F I68. 4 and 5.- The buffed tireI is shown mounted on a conventional retread tire building machine 10which is ordinarily employed for wrapping die sized rubber or camel backaround the tire, and includes a pair of idle mandrels 11 and 12 and amotor driven mandrel l3 engaging the beads 14 of the tire. One of themandrels is adjustable to permit mounting and removal of the tiretherefrom.

The fiberglass cords 7 which are to be wound about the tire may be usedas is, or first impregnated in known manner to provide a coating thereonfor protection against interfilament destructive action and enhance thebonding between'the glass fiber surfaces and the retread rubbermaterial. In any event, a plurality of single-cord serving packages 15are provided on a support stand 16 radially spaced from the tirebuilding machine, from which the individual cords 6 are passed through asystem of guide eyes 17 and individual adjustable tension controllingdevices 18 which allow the individual cords to be drawn from thepackages at different rates of speed to provide the different cordlengths required for uniform feed rotation of the tire being wrapped.Since the buffed surface 5 of the tire I is slightly round in crosssection, it will be apparent that the cords which are wrapped around thecenter of the buffed tire will be drawn forward at a greater rate ofspeed than the cords wrapped around the outside portions of the buffedtire surface.

After merging from the tensioning devices 18, the individual cords 7 arepassed through a warp guide or leveling reed 19 which serves to maintainthe cords in individually aligned positions and also provides ahorizontally level warp. Next the individual cords are threaded throughan adjustable width reed or comb rack 20 which also maintains theindividual positioning of the cords and allows for quick changing of theoverall width of each layer or belt in accordance with he width of thetires being retreaded. From there the individual cords layers passedover a amount of driven, reverse roll liquid cement coating device 21 ofconventional type which applies a suitable air drying cement 22 to thebottom surfaces only of the cords through contact with the upper roller23. Now the reinforcing cords 7 are carefully positioned on the buffedtire surface 5 with the desired spacing therebetween and the tire isslowly rotated at uniform speed to draw the cords onto the buffed tire.As the tire rotates, the cords pass beneath pressure rollers 24 whichpress the bottom most layer of cords firmly in position on the buffedtire surface, and each succeeding layer against the adjacent layertherebeneath. To obtain the desired zigzag pattern of the cord layers 6for proper crossover of the cords of each successive layer, the widthadjustable reed or comb rack 20 is slowly reciprocated back and forth asthe cords are wrapped onto the rotating tire. The rate of reciprocatingmotion of the adjustable width comb rack 20 will vary depending on therate of rotation of the tire and the desired cord angle, and isadjustable to produce a desired amount of horizontal displacement of thecord layers for a given amount of tire rotation, as for example, 1% inchhorizontal displacement of the entire cord layer or belt for each tirerotation. The reciprocating motion is continued until a sufficientweight and length of cord material has been wrapped around the tire toproduce the desired strength. As an example, it may be desired to apply2 pounds or approximately 2,550 yards of individual fiberglass tirecords to a typical heavy duty l0.00 20 buffed casing over a width of l0inches, in which event each layer of cord material of the preferred 10cords per inch in width would be approximately 9% cord layers, whichwould place the outer cord layers some distance from the buffed surfaceof the tire.

After the desired number of reinforcement cord layers 6 have beenapplied to the buffed surface and cemented down as just described, theentire belted portion of the tire is sprayed with a high qualityair-drying cement, which not only coasts the large portion of the buffedtire surface 5 left exposed after the cord layers have been applied, butalso coats the individual cords themselves to provide a substantialincrease in the surface area covered by the cement. This greatlyenhances the adhesive bond between the retread rubber which is laterapplied and the buffed tire, of which the cord layers are now a part.The latter cement coating may be applied while the tire I is still onthe machine 10 used for winding the reinforcement cords onto the tire,but it is preferably applied after the wrapped tire I has beentransferred to a conventional die sized rubber tire builder or striptire builder (not shown) so that the die sized or strip rubber can beimmediately applied thereafter.

During wrapping of the die sized or strip rubber about the belted casingl, rollers subject to high pressures contact the outer surface of therubber and press the rubber, which is then soft and uncured into andaround the individual cords of each layer. This occurs despite the factthat the outer layers are separated some distance from the buffedsurface of the tire because of the relatively open mesh pattern of thereinforcement layers. The net result is that there is an improvedadhesive bond between the tire and retread rubber because of theincreased surface area of the cords and buffed surface of the tirecovered by cement and contacted by the retread rubber, which is enhancedby a mechanical or interlocking connection between the open lattice cordlayers and the surrounding cured rubber. Since this latter interlockingconnection is positive in nature, it is unaffected by atmospheric orchemical variations that may serve to deteriorate the effectiveness ofthe cement bond, thus, ensuring against tread peel. The final step inthe retreading operation is to cure the retread rubber in a conventionalvulcanizing mold, during which the tread design is also formed in theouter surface of the retread rubber.

While the method just described in an effective and simple way ofapplying the reinforcement cords to a buffed tire surface, neverthelessit does require specialized equipment for producing the required cordpatterns, which makes it somewhat impractical for use by each of thethousands of existing tire retreading companies. However, thisrequirement may be obviated by making available to the individualretreaders prewound cord patterns held in place on continuous strips ofmold release paper of suitable type which will not adhere to the cementused in the retreading operation. The predetermined pattern ofreinforcing cords is maintained in fixed position on the release paperby chemically or mechanically eliminating the release film fromspaced-apart zones along the length of the release paper and placing onthe paper in those areas a narrow strip of adhesive which is sufficientto hold the cords in the proper relative position. The spacing andnumber of adhesive strips should be sufficient to provide the requiredpattern holding ability and still permit ready transfer of the cordpattern from the release paper to be cement coated buffed tire withoutthe release paper adhering to the cemented surface. Portions of theadhesive strips may be pulled from the surface of the release paper bycontact with the tire, but the composition of the cements used on therelease paper and tire may be similar so that no deterioration due tomixing of the cements will occur. While the width of the cement stripson the release paper and distance therebetween may vary widely, it willbe apparent that the less cement on the release paper, the less problemthere will be of the release paper adhering to the tire, but, of course,the cement strips must be adequate to maintain the relative positions ofthe cord patterns as aforesaid.

FIGS. 6 and 7 illustrate schematically the manner in which a particularcord pattern 25 may be adhered to a continuous length of release paper26 which is shown stored on a rotatable spool 27. The outer end of therelease paper is threaded between a plurality of horizontally spacedpairs of rolls 28 for pressing of the mutually parallel reinforcingcords 7 into contact with spaced apart adhesive strips 29 on the releasepaper as the release paper is pulled between the rolls and is woundabout a second spool 30. The number and spacing of the individual cordsapplied to the release paper maybe varied as desired, as may the cordpaper, which is controlled by passing the cords which are stored onindividual spools 31 through an adjustable width, reciprocable reed orcomb rack 32 to maintain the individual positioning of the cords andproduce a horizontal displacement of the cords to achieve the desiredzigzag pattern. Individual guide eyes 33 and tensioning devices 34 mayalso be provided for passage of the individual cords therethrough priorto passage through the comb rack 32.

The cord patterns thus preplaced on the release paper 26 may readily betransferred to a buffed casing 1 using conventional retreading equipment35 on which the buffed tire is mounted for rotation as shown in FIG. 8.As the buffed tire I is rotated, cement is sprayed over the entirebuffed surface 5 and the cord side of the release paper 26 is pressedagainst the cement coated surface as shown, after which the releasepaper is stripped away leaving the cord pattern in place on the tire.Care should be taken to pay the release paper out in a perfectlystraight line toward the buffed tire surface so that the cord pattern isaccurately reproduced on the tire. As each separate cord layer isapplied to the tire, the outer surface thereof is sprayed with cement bya spraying device 36 so that the next succeeding layer will properlyadhere thereto, and so on. When the desired number of cords layers hasbeen applied to the tire, the release paper is sheared through to cutthe individual cords 7, and the cord wrapped casing l is then wound withdie sized rubber or camel back, with sufficient pressure applied toforce the die sized rubber into and around the individual cord layers aspre iously described. Finally, the retread rubber is cured inconventional manner.

In still another form of the invention shown in FIG. 9, the desiredreinforcement cord pattern is first applied to a continuous thin strip37 of uncured rubber or other suitable elastomeric material which hasbeen extruded through a die of a conventional extruder 38 to produce therequired width of strip material for the particular tire beingretreaded. A typical strip emerging from the extruder 38 isone-sixteenth inch thick and 7% inches wide, and is supported by aseries of rollers 39. Individual reinforcement cords 7 are fed fromsuitable individual supply packages 40 into contact with the uppersurface 41 of the extruded rubber 37 and by means of nipper rolls 42 arelightly pressed into the rubber strip, which because of its soft,adhesive nature, will securely hold the cords in place. Thereinforcement cords are arranged in parallel fashion prior to contactingthe rubber strip 37 by a conventional adjustable reed or guide bar 43which may be adjusted to obtain any desired spacing or separationdistance between the cords. However, no more than one cord thickness canbe effectively bonded to the surface of the rubber strip in this manner,and accordingly, a neatly arranged shoulder to shoulder warp is themaximum allowable warp density. The lower limit of warp density willvary depending on the weight and strength of reinforcement cordsdesired.

The composite rubber and cord strip thus produced may be wound on a drumfor later use, or fed directly onto the buffed surface ofa tire I to beretreaded as shown in FIG. 9. The tire I is supported for rotation onthe rotatable mandrel 45 of conventional tire-building machine 46, andis sprayed with a suitable adhesive as it rotates past a spray nozzle47. For each complete rotation of the tire, a one sixteenth inchthickness of tread rubber strip with the reinforcement cords embedded inthe upper surface thereof is wrapped about the tire. After the desirednumber of spirally wound reinforcement cord layers is obtained (in thiscase six), the individual cords 7 are sheared by actuation of a knife48, but the strip rubber 37 without the cords embedded therein iscontinued to be spirally wrapped about the tire to obtain the finaldesired thickness of retread rubber, as shown in FIG. 10. Reinforcementcords are not placed throughout the total thickness of the retreadrubber since that would put a great many cords on or adjacent the outersurface of the tread where they would be distorted when the treadpattern was subsequently molded into the outer tread area. Accordingly,it is preferred that the cord layers be located no nearer to the outersurface of the tread rubber than the bottom of the tread pattern indentsto be subsequently formed therein. The cords 7 are desirably sheared ona bias to minimize weight variations caused by starting and terminatingthe cord feed. After the desired number of reinforced and nonreinforcedstrip layers have been wrapped about the buffed tire surface, the tireis bagged and placed in a mold for conventional curing of the retreadrubber.

This latter method of retreading tires, like the methods previouslydescribed, places the reinforcement cords 7 within be new tread rubberat some distance outward from the buffed tire surface where they aremost effective in preventing tread peel. In addition, however, thislatter method has several distinct advantages advantages over thepreviously discussed methods. Because the reinforcement cords arepressed into the outer surface, each reinforcement cord layer is alreadyseparated from the other and the individual cords are completelysurrounded by retread rubber material. Ac

cordingly, there is no need to maintain any particular spacing betweenthe cords, and the cords need not be angularly disposed in zigzagfashion, as is required by the other disclosed methods for completepenetration of the retread rubber throughout the cord layers. Thus, thereinforcement cords may be arranged continuously with substantially zeroangle between the cords and circumference of the tire, whereby the hightensile strength of the reinforcement cords may be employed to itsmaximum benefit.

Another advantage obtained with this latter method is increased impactresistance due to the cushioning effect of the strip rubber thicknessbetween each of the cord layers. In use, tires are subjected to frequentand severe impacts which cause deflection of the tire and high tensionin the fiberglass cords. Although fiberglass is relatively inextensible,having a maximum of 4 percent elongation prior to failure, because thereinforcement cords are separated by a thickness of rubber materialwhich is cushioning in nature, the cords will absorb greater impactwithout failure. While this effect is small for a single cord, it isgreatly magnified through the use of hundreds of cords arranged in asimilar fashion. When wound in a circumferential pattern such as iscommon in the filament winding method of producing circular reinforcedproducts, fiberglass strands can product from 250,000 to 300,000 lbs.per sq. in. of tensile strength. This compares favorably with the bettergrades of synthetic fiber such as rayon, nylon or polyester which havetensile strengths in the range of from 10,000 to 20,000 lbs. per sq. in.Thus, variations in the straight circumferential pattern for thefiberglass strands will still retain substantial strength advantagesover other known strands suitable for tire reinforcement.

One such variation is the employment of the zigzag pattern previouslydescribed. Rubber and strands made from synthetic resins are known fortheir ability to elongate prior to failure; elongation on the order ofpercent is common in such materials. Fiberglass is relativelyinextensible with a maximum of 4 to 6 percent stretch before failure.if, however, the fiberglass strands are arranged in the described zigzagpattern wherein they are disposed at an angle with respect to thecenterline of the tire, it will be apparent that some elongation will bepermitted by straightening of the fiberglass strands in the rubbermatrix.

From the foregoing, it will now be apparent that the placement ofreinforcement cords in thread rubber with thread rubber completelysurrounding the cords in the manner disclosed herein will greatly resistthread peel and add greater strength and stability in the thread rubber.By selectively placing the reinforcement cords as close as possible tothe outer surface of the thread portion of the tire in the mannerdescribed herein, outer thread stability is greatly improved, whichresults in much greater thread life. Thus, not only will the tire casinghave great hoop strength when wrapped with reinforcement cords in knownmanner, but the thread portion itself will have its own independent hoopstrength due to the reinforcement cords placed directly therein, whichgreatly reduces the chances of the thread peeling away from thereinforced tire casing. These same principles may also be advantageouslyused in strengthening the thread portion of new tire constructions.

lclaim:

1. In a tire comprising an inner annular casing portion and an outercircumferential thread portion; a plurality of circumferentiallydisposed reinforcement cords arranged in outwardly spirally wrappedlayers within said thread portion, said cords being continuousthroughout more than one of said spirally wrapped layers.

2. The tire of claim 1 wherein the cords in each layer are spaced apartfrom each other and are arranged in a symmetrical zigzag pattern, thespace around the cords being filled by the material of said threadportion.

3. The tire of claim 1 wherein the cords in each layer are spaced apartfrom each other and are arranged in a symmetrical zigzag pattern withadjacent layers crisscrossing each other to provide space around hecords in each layer which is filled by the material of said threadportion.

4. The tire of claim 1 wherein each layer of reinforcement cords isseparated by a layer of the material of said thread portion.

5. The tire of claim 1 wherein said thread portion consists of outwardlyspirally wrapped layers off elastomeric material in which saidreinforcement cords are embedded.

6. The tire of claim 1 wherein the angle of wrap of said cords withrespect to the peripheral centerline of said tire continuously reverses.

7. The tire of claim 1 wherein said reinforcement cords consist offiberglass strands.

8. The tire of claim 1 wherein the cords in each layer have a spacing ofapproximately l0 cords per inch of width to expose a substantial portionof the outer surface of said casing portion for direct contact by saidtread portion.

7. The tire of claim 1 wherein said tread portion has a tread pattern inthe outer periphery thereof and said spirally wrapped layers extend fromthe outer ply of said inner annular casing portion to the bottom of saidtread pattern uniformly distributing said reinforcement cords throughoutsaid tread portion.

10. In a tire comprising an inner annular casing portion and an outercircumferential tread portion having a tread pattern in the outerperiphery thereof, a plurality of circumferentially disposedreinforcement cords embedded throughout the tread portion from the outerply of said inner annular casing portion to the bottom of said treadpattern.

11. The tire of claim 10 wherein said reinforcement cords are arrangedin a plurality of outwardly spirally wound layers, said cords in eachlayer being spaced apart from each other and arranged in a symmetricalzigzag pattern with adjacent layers crisscrossing each other to providespace around the cords in each layer whichis filled by the material ofsaid tread portion.

12. The tire of claim 10 wherein said tire is a retreaded tire.

13. A retreaded tire comprising a tire casing having an outer smoothsurface and a newly applied tread portion bonded thereto, said treadportion having a plurality of circumferentially disposed reinforcementcords arranged in a plurality of outwardly spiraled wound layers withinsaid tread portion, said cords being continuous throughout more than oneof said spirally wound layers.

14. The tire of claim 13 wherein said reinforcement cords are separatedfrom each other by the material of said tread portion.

15. The tire of claim 13 wherein said tread portion consists of aplurality of inner circumferential spirally overlying wraps ofcontinuous tread material each having a cord layer embedded in the outersurface thereof, and a plurality of outer circumferential spirallyoverlying wraps of tread material surrounding said inner wraps, saidouter and inner wraps having been cured to provide a unitaryconstruction with the tread pattern indents in said outer layers only.

16. The tire of claim 13 wherein the cords in each layer are spacedapart from each other and arranged in a zigzag pattern with the cords inadjacent layers crisscrossing each other to provide room therebetweenfor penetration of the material of the tread portion into and throughthe cord layers and substantial direct contact of the tread portion withthe outer smooth surface of said tire casing.

17. The tire of claim 16 further comprising an adhesive coating on saidouter surface of said tire casing and on said cords which provides anadhesive bond between the tread portion and said cords and the outersurface of said tire casing.

1. In a tire comprising an inner annular casing portion and an outercircumferential tread portion; a plurality of circumferentially disposedreinforcement cords arranged in outwardly spirally wrapped layers withinsaid tread portion, said cords being continuous throughout more than oneof said spirally wrapped layers.
 2. The tire of claim 1 wherein thecords in each layer are spaced apart from each other and are arranged ina symmetrical zigzag pattern, the space around the cords being filled bythe material of said tread portion.
 3. The tire of claim 1 wherein thecords in eacH layer are spaced apart from each other and are arranged ina symmetrical zigzag pattern with adjacent layers crisscrossing eachother to provide space around the cords in each layer which is filled bythe material of said tread portion.
 4. The tire of claim 1 wherein eachlayer of reinforcement cords is separated by a layer of the material ofsaid tread portion.
 5. The tire of claim 1 wherein said tread portionconsists of outwardly spirally wrapped layers of elastomeric material inwhich said reinforcement cords are embedded.
 6. The tire of claim 1wherein the angle of wrap of said cords with respect to the peripheralcenterline of said tire continuously reverses.
 7. The tire of claim 1wherein said reinforcement cords consist of fiberglass strands.
 8. Thetire of claim 1 wherein the cords in each layer have a spacing ofapproximately 10 cords per inch of width to expose a substantial portionof the outer surface of said casing portion for direct contact by saidtread portion.
 9. The tire of claim 1 wherein said tread portion has atread pattern in the outer periphery thereof and said spirally wrappedlayers extend from the outer ply of said inner annular casing portion tothe bottom of said tread pattern uniformly distributing saidreinforcement cords throughout said tread portion.
 10. In a tirecomprising an inner annular casing portion and an outer circumferentialtread portion having a tread pattern in the outer periphery thereof, aplurality of circumferentially disposed reinforcement cords embeddedthroughout the tread portion from the outer ply of said inner annularcasing portion to the bottom of said tread pattern.
 11. The tire ofclaim 10 wherein said reinforcement cords are arranged in a plurality ofoutwardly spirally wound layers, said cords in each layer being spacedapart from each other and arranged in a symmetrical zigzag pattern withadjacent layers crisscrossing each other to provide space around thecords in each layer which is filled by the material of said treadportion.
 12. The tire of claim 10 wherein said tire is a retreaded tire.13. A retreaded tire comprising a tire casing having an outer smoothsurface and a newly applied tread portion bonded thereto, said treadportion having a plurality of circumferentially disposed reinforcementcords arranged in a plurality of outwardly spirally wound layers withinsaid tread portion, said cords being continuous throughout more than oneof said spirally wound layers.
 14. The tire of claim 13 wherein saidreinforcement cords are separated from each other by the material ofsaid tread portion.
 15. The tire of claim 13 wherein said tread portionconsists of a plurality of inner circumferential spirally overlyingwraps of continuous tread material each having a cord layer embedded inthe outer surface thereof, and a plurality of outer circumferentialspirally overlying wraps of tread material surrounding said inner wraps,said outer and inner wraps having been cured to provide a unitaryconstruction with the tread pattern indents in said outer layers only.16. The tire of claim 13 wherein the cords in each layer are spacedapart from each other and arranged in a zigzag pattern with the cords inadjacent layers crisscrossing each other to provide room therebetweenfor penetration of the material of the tread portion into and throughthe cord layers and substantial direct contact of the tread portion withthe outer smooth surface of said tire casing.
 17. The tire of claim 16further comprising an adhesive coating on said outer surface of saidtire casing and on said cords which provides an adhesive bond betweenthe tread portion and said cords and the outer surface of said tirecasing.